A flash memory device may be included in a portable storage device. The portable storage device may include a flash translation layer (FTL), which may provide a mapping table that translates a logical address from a file system to a physical address of the flash memory device. The mapping table may be stored in a volatile memory of a memory controller and thus the mapping table may be lost when a power fails or is suddenly removed. Therefore the memory controller may flush the mapping table to the flash memory device whenever the mapping table is updated so that the mapping table may be recovered from the flash memory device after power is restored.